Cabinet for radio apparatus



Jan. 23, 1951 J REID ET AL 2,539,327

CABINET FOR RADIO APPARATUS Filed July 23, 1947 2 Sheets-Sheet 1 flyi It W16 Jay. 3

/15 if 19 zs E (28 25 INVENTOR. 5 Pe/d BY P /F6 5 0/52" Jan. 23, 1951 J.D. REID ET AL 2,539,327

CABINET FOR RADIO APPARATUS Filed July 23, 1547 2 Sheets-Sheet 2 Mo? mag0 Patented Jan. 23, 1951 CABINET FOR RADIO APPARATUS John Drysdale Reidand Paul F. G. Holst, Mount Healthy, Ohio, assignors to AVCOManufacturing Corporation, Cincinnati, Ohio, a corporation of DelawareApplication July 23, 1947, Serial No. 762,848

2 Claims.

This invention relates to radio cabinets and especially to cabinets inwhich loud speakers are to be housed. In the construction of radioreceiving sets and other sound reproducing apparatus the conventionalpractice has been to mount the speaker on the front panel of the radiocabinet so that the sound waves are directed through an opening in thepanel into the interior of the room in which the cabinet is located.This design, while conventional, is not entirely satisfactory, both fromthe styling standpoint and because the sound emitted from the cabinet isunevenly distributed and appears to come from a point source. Morespecifically, with this conventional arrangement, the high audiofrequencies are concentrated in a slender cone perpendicular to thefront panel, thereby imparting an undesirable characteristic which iscommonly known as directivity to the sound emanating from the cabinet.

An object of this invention is to provide a radio cabinet having a novelspeaker arrangement therein, whereby the conventional grill on the frontpanel of the cabinet may be omitted and the front of the cabinet closedso that the cabinet may be constructed in the form of an article offurniture not obviously containing a radio receiver.

Another object of this invention is to provide a radio cabinetconstructed and arranged to minimize the eifect of a point source ofsound.

A further object of this invention is to pro-v vide a radio cabinet soarranged that the sound waves emitted from the cabinet are more evenlydistributed throughout the room in which the cabinet is placed than ispossible with conventional cabinets.

A particular object of this invention is to provide a radio cabinethaving a speaker arranged and constructed to direct sound waves to therear of the cabinet in such a manner that the sound waves will bereflected from a boundary of the room adjacent the rear of the cabinet.

Another object of this invention is to provide a. radio cabinet having aloud speaker operatively connected to a. source of high frequency audiosignals and directed upwardly and to the rear of said cabinet and asecond loud speaker operatively connected to a source of low frequencyaudio signals and directed to the rear of said cabinet.

A still further object of this invention is to provide a soundreproducing system in which the interaction between the different soundfrequencies is minimized.

The novel features that we consider characteristic of our invention areset forth in the appended claims. The invention itself, however, both asto its organization and its method of operation, together withadditional objects and advantages thereof, will best be understood fromthe following description of four specific embodiments thereof when readin conjunction with the accompanying drawing, in which:

Fig. i is a perspective view of a radio cabinet constructed inaccordance with the principles of the invention, illustrating the closedfront exterior construction.

Fig. 2 is a sectional elevation of a device illustrating the preferredarrangement of the receiver chassis and speaker within the cabinet.

Fig. 3 is a rear view of the cabinet shown in Fig. 2 furtherillustrating the arrangement of the receiver chassis and speaker withinthe cabinet.

Fig. 4 is a vertical section from the front to the rear of a radiocabinet, illustrating a modified embodiment of this invention.

Fig. 5 is a rear view of the modified form shown in Fig. 4.

Fig. 6 is a vertical section from the front to the rear of a radiocabinet illustrating a third form of the invention including twospeakers for directing soundwave to the rear of the cabinet.

Fig. 7 is a rear view of the cabinet of Fig. 6, further illustrating thearrangement of the receiver chassis and speakers within the cabinet.

' Fig. 8 is a vertical section from the front .to the rear of thecabinet, illustrating a second dual speaker arrangement Within thecabinet.

Fig. 9 is a rear view of the modified form shown in Fig. 8.

Fig; 1i] is a schematic diagram in block form of a radio circuitarrangement for use in con nection with the dual speaker arrangementsshown in Figs. 6 through 9.

Referring to Fig. 1, numeral 8 indicates generally a radio cabinethaving a closed front construction in accordance with the principles ofthis invention. A pair of doors in and H may be provided to permitaccess to the storage space within the interior of the cabinet. Itshould be understood, however, that the operation of the reproducer isin no manner dependent upon whether or not these doors are open orclosed. Suitable controls 12 and 13 for controlling the radio circuitsmay extend through the front wall as shown. It will also be understoodthat suitable decorative carving, paneling, inlaying or embossing (notshown) may be provided on the doors I and II as well as the remainder ofthe cabinet. I

In Fig. 2 a preferred arrangement of the loud speaker I4 and receiverchassis I5 within the cabinet is shown. A sound baflie I6 extendsdownward from the front to the rear of the cabinet. A second soundbaflie I! which contacts the lower edge of bafile I6 is employed toincrease the bafile area. The baffle I! may also constitute or be a partof the rear wall (not shown) if desired.

A horizontal shelf I9 extending across the cabinet adjacent the upperend of baflle I6 is employed to support a radio receiver chassis I5 inthe upper portion of the cabinet. Speaker I4 is mounted upon baflie ISin any suitable manner as by means of conventional bolts (not shown). Anopening is provided in bafile I6 and an acoustic horn 23 is sopositioned that the center of the loud speaker is covered by the throatof the horn. As shown, the horn preferably extends a short distancebeyond the rear of the cabinet, and functions to conduct high frequencysound waves from speaker I4 in an upward direction to a locationadjacent the rear of the cabinet. It will be understood that differenttypes of horns may be used such as conical, parabolic, or exponential.Satisfactory results have been obtained, however, by use of a simpleconical horn.

Referring to Fig. 3, baflle I6 is disposed within cabinet 3 in suchmanner that speaker I4 and horn 23 are located in the immediate vicinityof one of the end walls 24 of the cabinet. A Vertical wall 22 isprovided to separate the speaker from the rest of the cabinet. Wall 22preferably extends vertically fromshelf I9 to the bottom'of cabinet andis used to support one side of baflie I6. In this arrangement it isnecessary to use only the single additional vertical wall 22 which ahorn. While the preferred embodiment of the invention utilizes the hornconstruction as shown in Figs. 2 and 3, it has been found that suitableresults may be obtained by mounting the speaker as shown in Fig. 4. Sucha mounting is advantageous in that it provides for a maximum storagespace within the cabinet. Speaker I4, which is inclined upwardly and tothe rear of the cabinet, is preferably supported by a baffle 25 which inturn is mounted on vertical wall 26 and horizontal wall 21 by means of apair of suitable rails 28 and 29, which may be secured to the cabinet bymeans of screws, glue or in any suitable fashion. An opening 30 isprovided in rear wall 26 to permit passage of sound waves from thespeaker to the exterior of the cabinet. The baflle 25, the top .wall 27,and the back wall 26 are constructed to provide a continuous baflle.While it is preferable to place the opening in the rear wall of thecabinet, it will readily be understood that the opening may be providedin the upper wall of the cabinet rather than the rear wall or open: ingsmay be provided in each such wall for the passage of sound waves fromthe cabinet. A horizontal shelf I9 serves to support the radio chassisI5 as shown.

In Figs. 6 and 7 an alternative embodiment of the invention is shown,illustrating an arrange cooperates with the end wall 24 of the cabinet,

cation along the longitudinal axis of the cabin'etand need not be placedin the immediate vicinity of one end of the cabinet as shown. By

placing the speaker in the location illustrated, maximumunbroke'nstorage'space is provided within the cabinet and the need foran additional vertical wall similar to wall 22 is elimii nated. End wall24 functions not only as an end wall of the cabinet, but also acts toincrease the baffle area, thereby minimizing construction costs of acabinet assembled in accordance with the principles of this invention.As shown in Figs. 2 and 3, horn 23 preferably extends upwardly andoutwardly from the interior of the cabinet so as to direct highfrequency sound waves emitting from speaker I4 to the exterior of thecabinet in such a manner that the waves are first directed away from thelistener and will be reflected upwardly upon contact with the wall ofthe room to the rear of thecabinet. While it has been found to beadvantageous to direct the sound waves upwardly and to the rear in adirect substantially straight-line path, it. will be understood thatspeaker I4 may be arranged so that it directs sound waves sidewardly,rearwardly or downwardly. If desired, a curved conduit may be used toconduct sound waves from the speaker to the rear of the cabinet. InFigs. 4-and 5 there is shown an alternative embodiment of :theinvention; in..which the. speaker I4 is mounted inthe upper rearcornerof the cabinet and .which eliminates the need for within thecabinet. A support housing 49 mounted on the rear wall 48 ofthe cabinetfunctions as a sound baflle and serves to fixedly posi-' tion anupwardly facing speaker 43 within the cabinet. Conventional bolts (notshown) or any other suitable means may be employed to mount the speakerto the support. A horizontal shelf 4I serves as a support for a radiochassis and functions to seal the upper and lower portions of theinterior of the cabinet from each other. An acoustical horn 46 extendsthrough openings provided in shelf 4i and housing 41] with the throat 45of the horn formed by the opening in the housing 413. As shown, throat45 opens into the upwardly extending acoustical horn 45, the upper endof which is curved to direct sound waves upwardly and to the rear of thecabinet. Horn 46 may be" mounted to the rear wall 48 by means of clamps(not shown) or-may be sup ported from shelf 4|, or both, and may besealed about the opening in shelf III to avo.d leakage of low frequencysound wave'sthrough the open-' The radio cabinet, as shown in Figs. 6and 7,

includes arear wall 48 extending in a vertical diknown in the art, theenclosure in which speaker 49'is placed may be considered as an infinitebafile which insures a good low frequency response.

As stated in connection with Figs. 2 and 3, the

. horn may be conical, parabolic or exponential.

Best results, however, have been obtained by use of an exponential hornwhich is noted for its uniform frequency characteristics and sharp lowfrequency cut-off, which cause the horn to act as a high-pass'filter. Inthis manner, soundwaves' having a greater frequency than the cut-off-frequency of the horn are passed through thehorn while those having afrequency less than the cutof! frequency of the horn are filtered outand are prevented from passing therethrough. It has been found desirableto provide a horn having a cut-off frequency of approximately 250 cyclesper second or less.

The radio receiver chassis 42 shown in Fig. .6 is constructed andarranged to provide a source of low frequency audio signals, and aseparate source of high frequency audio signals. Speaker 43 isoperatively connected to the source of high frequency audio signalswhile speaker 49 is operatively connected to the source of low frequencyaudio signals. As shown in Figs. 6 and '7, both the high and lowfrequency speakers 43 and 49 are disposed within the cabinet in theimmediate vicinity of the end wall 59 of the cabinet. In thisarrangement it is necessary to use only the single additional wall 52which together with baffle 4|, wall 50, and bottom 5!, seals off thespeaker compartment from the rest of the cabinet. It will be understood,however, that speaker 43, acoustical horn 4B and speaker 49 may bedisposed in any desirable location along the rear wall of the cabinetand need not be placed in the immediate vicinit-y of end wall as shown.In the embodiment illustrated, end wall 59 functions not only as an endwall of the cabinet, but also acts as one side of the enclosure in whichspeaker 49 is placed. In this manner, construction costs of the cabinetare minimized.

In Figs. 8 and Qthere is shown a further alternative embodiment of theinvention in which a speaker 60 is mounted in the upper rear corner ofthe cabinet, and which eliminates the need for a horn. While the use ofa born as shown in Fig. 6 is preferred, it has been found that suitableresults may be obtained by mounting the speaker as shown in Fig. 8. Itwill readily be apparent that the embodiment shown in Fig. 8 isadvantageous in that it requires less space and is less costly toproduce. A second speaker 81 is mounted upon the rear wall 62 of thecabinet within a sealed enclosure as set forth in connection with Figs.6 and 7, speakers 5s and 5 i being operatively connected to suitablesources of high and low frequency audio output respectively. Speaker 60,which is mounted on a baffle 63 is inclined upwardly and to the rear ofthe cabinet and is preferably retained in contact with vertical wall 52and the horizontal wall 64 by means of a pair of suitable rails 85 and66. A horizontal shelf 61 serves to seal oi the upper portion of the Iinterior of the cabinet from the lower portion thereof, and also tosupport the radio chassis 68. A vertical wall 69. together with thebottom H, the front 10, the rear wall 52 and shelf 61 serve to providean enclosure in which speaker 6| is housed, with the beneficial resultsalready noted.

In Fig. 10 there is shown a schematic diagram in block form of a radioreceiver system providing two independent circuits which constitutesources of relatively high and low frequency audio output. Such circuitsare known in the art and do not constitute a part of this invention. Thecircuit shown is merely illustrative of one circuit which may beemployed in connection with this invention. A particular circuit whichmay be employed in connection with this invention is fully shown in ourU. S. Patent No. 2,474,191. As shown, the circuits may be operativelyconnected to either a phonograph input 80 or a radio input 8| by meansof a suitable switch 82.

Signals entering switch 82 pass through a volume control 83 and a firstaudio frequency amplifier 84 from which they are conducted to a low-passfilter 85 and a high-pass filter 86. The cut-off frequencies of thesefilters may be of any desired frequency such as 250 cycles per second.Signals having frequencies above the cut-off frequency of filter 8B areconducted to an audio amplifier 8! from which they are conducted to aloud speaker 88, whereby the signals are converted to sound waves.Signals having a frequency below the cut-off frequency of filter 85 areconducted to audio amplifier 89 and thence to loud speaker 90 wherebythey are converted to sound waves.

In the assemblies shown in Figs. 6 through 9, speakers is and El areconnected to a source of low frequency signals, for example, signalshaving a frequency less than 250 cycles persecond, while speakers 43 andare conn cted solely to a source of high frequency which may beconsidered, for example, to be signals of a frequency in excess of 25-0cycles per second. The speakers l4 of Figs. 2 through 5 are, of course.

\ connected to sources of both high and low frequency signals.

In operation, the radio cabinet is normally positioned with its rearwall adjacent but slightly spaced from a wall of the room in which it isplaced. High frequency sound waves from speakers 14, 43 and 50 aredirected upwardly and to the rear of the cabinet and are reflectedupwardly and outwardly into the room by the wall adjacent the rear ofthe cabinet. Low frequency sound waves from speaker 14 upon striking thewall of the room adjacent the speaker are dispersed through deviouspaths and do not tend to travel upwardly and outwardly into the room ina straight-line path as do the high frequency sound waves. The lowfrequency sound waves emitted by speakers 49 and BI are to a largedegree separated from the high frequency sound waves emitting fromspeakers 43 and 68, and enter the room through paths of their ownchoosing.

It is known that high frequency sound waves normally travel in asubstantially straight-line path while low frequency sound Waves do notso travel. It will readily be understood, therefore, that high frequencywaves will be reflected upwardly in the direction of the ceiling of theroom and will then be reflected from the ceiling of the room anddispersed to greater extent than is the case with a conventional loudspeaker arrangement. More specifically, the high frequency waves aredirected upwardly and to the .rear of the cabinet, while the lowfrequency waves are directed primarily to the rear of the cabinet. Sinceit is the high frequency sound waves which are largely responsible forthe directivity of conventional radio receiver sets, and since there hasthus been provided a radio cabinet constructed and arranged to provide amaximum dispersion of the high frequency sound waves, the effect ofdirectivity has been greatly reduced.

It will be observed that there has thus been provided a novel radiocabinet and speaker construction incorporating the features of maximumstorage space, a closed front panel which need not be opened when theradio is operated, and a construction which directs the sound wavesemitting therefrom in a direction upwardly and rearwardly from the frontof the cabinet, whereby the sound waves are reflected upon contact withobjects such as the wall of the room to the rear of the cabinet. In thismanner, the sound waves emitted from the cabinet reach the listenerthrough devious paths, thereby greatly minimizingthe effect of a pointsource of sound as compared to that emitted by conventional radiocabinet and receiver arrangements.

It will also be observed that the intermodulation between high and lowfrequencies normally incident to audio amplifiers and speakers withconventional systems which reproduce the entire audio range will begreatly diminished in a dual channel system as described herein.

While this invention has been shown and described in four embodimentsthereof, it will be understood that various modifications and changesmay be made therein coming within the scope of the appended claims.

What is claimed is:

i 1. In a sound reproducing device to be positioned adjacent the wall ofa room, a cabinethaving an acoustically closed front wall normallypresented to a listener, vertically extending side walls, top and bottomwalls, and a rear wall normally presented to said room wall, an upwardlyinclined baflle extending from said rear wall to said top wall, a,horizontally disposed bafiie extending from said rear wall to said frontwall for dividing said cabinet into upper and lower acousticallyinsulated compartments, openings in said rear wall above and below saidhorizontal bafile, respectively, for permitting the emission of soundfrom said compartments, an opening in said inclined baffle, a loudspeaker mounted upon said inclined bafiie with the mouth of said speakerin reg istry with said bafile opening, said speakermouth facing saidupper compartment opening in a direction upwardly and rearwardly of saidcabinet whereby sound waves from said speaker are projected against saidroom all in a direction upwardly and rearwardly of said cabinet, asecond speaker mounted upon said cabinet rear wall and near one of saidend walls with the mouth of said speaker in registry with said lowerrear wall opening whereby sound waves from said speaker are'projectedagainst said room wall in a direction horizontal and to'the rear of saidcabinet, a vertically disposed baille extending from said bottom wall tosaid horizontally disposed bafile and between said second speaker andthe other of said end walls, a frequency selective network for providingaudio frequency signals of a predetermined minimum frequency operativelyconnected to said first speaker, and a frequency selective network forproviding audio frequency signals of a predetermined maximum frequency 8operatively connected to said second speaker, the maximum frequency ofthe audio signals furnished by said second-mentioned network being nogreater than the minimum frequency of the audio signals furnished bysaid first-mentioned network.

2. In a sound reproducing device to be positioned adjacent the wall of aroom, a cabinet having an acoustically closed front wall normallypresented to a listener, vertically extending side walls, top and bottomwalls, and a rear wall normally presented to said room wall, an upwardlyinclined baflle extending from said rear wall to said top wall, ahorizontally disposed baffle extending from said rear wall to said frontwall'for dividing said cabinet into upper and lower acousticallyinsulated compartments, openings in said rear wall above and below saidhorizontal baflle, respectively, for permitting the emission of soundfrom said compartments, an opening in said inclined bafile, ahigh-frequency loud speaker mounted upon said inclined bafile with themouth of said speaker in registry with said baffle opening, said speakermouth facing said upper compartment opening in a direction upwardly andrearwardly of said cabinet whereby sound waves from said speaker areprojected against said room wall in a direction upwardly and rearwardlyof said cabinet, a low-frequency speaker mounted upon said cabinet rearwall and near one of said end walls with the mouth of said speaker inmg. istry with said lower rear wall opening whereby sound waves fromsaid speaker are projected against said room wall in a directionhorizontal to the'rear of said cabinet, and a vertically disposed bafileextending from said bottom wall to said horizontally disposed baffle andbetween said lowfrequency speaker and the other of said end walls.

JOHN DRYSDALE REID. PAUL F. G. I-IOLS T.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Karnes July 26, 1938

